Calibration of sensor arrays

Abstract

Systems and methods for calibrating sensor arrays. An exemplary system measures a distance to a target object with the sensors. The system calculates a first position of the target object based on measurements from a first pair of the sensors and calibrated sensor coordinates for the first pair, calculates a second position of the target object based on measurements from a second pair of the sensors and the calibrated sensor coordinates for the second pair, and calculates a third position of the target object based on measurements from a third pair of the sensors and the calibrated sensor coordinates for the third pair. The system then compares the first position, the second position, and the third position calculated for the target object, and determines that the calibrated sensor coordinates for one or more of the sensors are inaccurate if a difference between the first, second, and third positions exceeds a threshold.

The invention claimed is: 
     
       1. An apparatus comprising:
 a sensor array comprising at least three sensors each configured to measure a distance to a target object in a two-dimensional (2D ) coordinate system, wherein calibrated sensor coordinates in the 2D coordinate system are determined for each of the sensors during calibration; and 
 a controller configured to calculate a first position of the target object in the 2D coordinate system based on measurements from a first pair of the sensors and the calibrated sensor coordinates for the first pair of the sensors, to calculate a second position of the target object in the 2D coordinate system based on measurements from a second pair of the sensors and the calibrated sensor coordinates for the second pair of the sensors, and to calculate a third position of the target object in the 2D coordinate system based on measurements from a third pair of the sensors and the calibrated sensor coordinates for the third pair of the sensors, 
 wherein the controller is configured to compare the first position, the second position, and the third position calculated for the target object, and to determine that the calibrated sensor coordinates are inaccurate if a difference between the first position, the second position, and the third position exceeds a threshold. 
 
     
     
       2. The apparatus of  claim 1  wherein:
 the controller is configured to adjust the calibrated sensor coordinates for at least one sensor responsive to a determination that the calibrated sensor coordinates are inaccurate. 
 
     
     
       3. The apparatus of  claim 1  wherein:
 the controller is configured to verify the calibrated sensor coordinates are accurate if the difference between the first position, the second position, and the third position does not exceed the threshold. 
 
     
     
       4. The apparatus of  claim 3  wherein:
 the controller is configured to provide an indication to an operator if the calibrated sensor coordinates for the sensors are verified as accurate. 
 
     
     
       5. The apparatus of  claim 1  wherein:
 the sensors comprise acoustic sensors. 
 
     
     
       6. A method for calibrating a sensor array comprised of at least three sensors, the method comprising:
 measuring a distance to a target object in a two-dimensional (2D) coordinate system with each of the sensors, wherein calibrated sensor coordinates in the 2D coordinate system are determined for each of the sensors during calibration; 
 calculating a first position of the target object in the 2D coordinate system based on measurements from a first pair of the sensors and the calibrated sensor coordinates for the first pair of the sensors; 
 calculating a second position of the target object in the 2D coordinate system based on measurements from a second pair of the sensors and the calibrated sensor coordinates for the second pair of the sensors; 
 calculating a third position of the target object in the 2D coordinate system based on measurements from a third pair of the sensors and the calibrated sensor coordinates for the third pair of the sensors; 
 comparing the first position, the second position, and the third position calculated for the target object; and 
 determining that the calibrated sensor coordinates are inaccurate if a difference between the first position, the second position, and the third position exceeds a threshold. 
 
     
     
       7. The method of  claim 6  further comprising:
 adjusting the calibrated sensor coordinates for at least one sensor responsive to a determination that the calibrated sensor coordinates are inaccurate. 
 
     
     
       8. The method of  claim 6  further comprising:
 verifying the calibrated sensor coordinates are accurate if the difference between the first position, the second position, and the third position does not exceed the threshold. 
 
     
     
       9. The method of  claim 8  further comprising:
 providing an indication to an operator if the calibrated sensor coordinates are verified as accurate. 
 
     
     
       10. The method of  claim 6  wherein:
 the sensors comprise acoustic sensors. 
 
     
     
       11. An apparatus comprising:
 a sensor array comprising at least four sensors each configured to measure a distance to a target object in a three-dimensional (3D) coordinate system, wherein calibrated sensor coordinates in the 3D coordinate system are determined for each of the sensors during calibration; and 
 a controller configured to calculate a first position of the target object in the 3D coordinate system based on measurements from a first set of the sensors and the calibrated sensor coordinates for the first set, to calculate a second position of the target object in the 3D coordinate system based on measurements from a second set of the sensors and the calibrated sensor coordinates for the second set, to calculate a third position of the target object in the 3D coordinate system based on measurements from a third set of the sensors and the calibrated sensor coordinates for the third set, and to calculate a fourth position of the target object in the 3D coordinate system based on measurements from a fourth set of the sensors and the calibrated sensor coordinates for the fourth set; 
 wherein the controller is configured to compare the first position, the second position, the third position, and the fourth position calculated for the target object, and to determine that the calibrated sensor coordinates are inaccurate if a difference between the first position, the second position, the third position, and the fourth position exceeds a threshold. 
 
     
     
       12. The apparatus of  claim 11  wherein:
 the controller is configured to adjust the calibrated sensor coordinates for at least one sensor responsive to a determination that the calibrated sensor coordinates are inaccurate. 
 
     
     
       13. The apparatus of  claim 11  wherein:
 the controller is configured to verify the calibrated sensor coordinates are accurate if the difference between the first position, the second position, the third position, and the fourth position does not exceed the threshold. 
 
     
     
       14. The apparatus of  claim 13  wherein:
 the controller is configured to provide an indication to an operator if the calibrated sensor coordinates are verified as accurate. 
 
     
     
       15. The apparatus of  claim 11  wherein:
 the sensors comprise acoustic sensors. 
 
     
     
       16. A method for calibrating a sensor array comprised of at least four sensors, the method comprising:
 measuring a distance to a target object in a three-dimensional (3D) coordinate system with each of the sensors, wherein calibrated sensor coordinates in the 3D coordinate system are determined for each of the sensors during calibration; 
 calculating a first position of the target object in the 3D coordinate system based on measurements from a first set of the sensors and the calibrated sensor coordinates for the first set; 
 calculating a second position of the target object in the 3D coordinate system based on measurements from a second set of the sensors and the calibrated sensor coordinates for the second set; 
 calculating a third position of the target object in the 3D coordinate system based on measurements from a third set of the sensors and the calibrated sensor coordinates for the third set; 
 calculating a fourth position of the target object in the 3D coordinate system based on measurements from a fourth set of the sensors and the calibrated sensor coordinates for the fourth set; 
 comparing the first position, the second position, the third position, and the fourth position calculated for the target object; and 
 determining that the calibrated sensor coordinates are inaccurate if a difference between the first position, the second position, the third position, and the fourth position exceeds a threshold. 
 
     
     
       17. The method of  claim 16  further comprising:
 adjusting the calibrated sensor coordinates for at least one sensor responsive to a determination that the calibrated sensor coordinates are inaccurate. 
 
     
     
       18. The method of  claim 16  further comprising:
 verifying the calibrated sensor coordinates are accurate if the difference between the first position, the second position, the third position, and the fourth position does not exceed the threshold. 
 
     
     
       19. The method of  claim 18  further comprising:
 providing an indication to an operator if the calibrated sensor coordinates are verified as accurate. 
 
     
     
       20. The method of  claim 16  wherein:
 the sensors comprise acoustic sensors.